1. Field of the Invention
The present invention is generally directed to a label applicator which applies a label to an article moving along a known travel path. More particularly, the present invention relates to a label applicator which is used to apply shipping labels to articles being transported on a conveyor system. Most particularly, the label applicator of the present invention finds use in the application of shipping labels to tops of articles of varying heights being carried on high throughput conveyor systems.
2. Description of the Prior Art
The use of automated labeling equipment for applying labels to moving, conveyor borne articles is known in the art. In one known system, the label is first printed with various label information by a label printer and the printed label is presented at the feed position where it is then retained against a grid by means of a vacuum. When the object to be labeled is moved into alignment with the label applicator, a blast of gas transfers the label to the article. One such prior art arrangement is shown in U.S. Pat. No. 3,329,550, which issued on Jul. 4, 1967.
However, when labels are to be applied to the top surfaces of packages of varying heights it is desirable to move the label retaining grid into closer proximity to the surface of the article to be labeled. One prior art device teaches the use of a plurality of hollow vacuum fingers which transfer a label to a surface and apply it by contact with the surface or with an air blast. This arrangement is disclosed in U.S. Pat. No. 4,729,362, which issued on Apr. 24, 1973. While this arrangement is satisfactory in some applications, it does not accommodate large variances in article heights.
Other label applicators, such as that disclosed by U.S. Pat. No. 4,615,757, which issued on Oct. 7, 1986, utilize a label printer mounted for horizontal movement above the conveyor with a gravity biased label applying arm which drops into contact with the article to apply the label. U.S. Pat. No. 5,232,539 discloses a movable printer/applicator head which is mounted over a conveyor and travels vertically along a fixed path to apply labels to articles of different heights.
In all of the prior art label applicators for applying labels to the tops of articles, the label printer and/or applicator are suspended above the conveyor path. This necessitates special handling for oversized packages which cannot pass beneath the labeling equipment. Additionally, the prior art label applicators which are mounted above the conveyor for top labeling of articles must travel from the label printer, which is located at a point above the maximum package height, down to the top surface of the package to apply the label, and then return to the printer for the next label. In systems where the label printer is combined with the applicator and is moved, either horizontally or vertically, into proximity with the package surface to be labeled, moving the mass of the label printer itself up and down to accommodate the various package heights requires heavy duty equipment for rapidly accelerating and decelerating the entire printer/applicator mass in high throughput applications.
Additionally, most of the prior art label printer/applicator assemblies use label stock wound on a supply reel and the spent backing strip is wound onto a take-up reel. The quantity of labels is limited by the size of the supply reel which can be accommodated by the equipment. Each time the supply reel runs out of stock, a new reel of label stock must be installed and threaded through the printer. The reels of spent backing paper must also be periodically removed.
Preferably, to maintain a high throughput of articles on the conveyor, the time between the time the application of labels on successively appearing products of different heights will be less than 1.0 seconds. Down time for adding new label stock must also be minimized.